Using CDN.net with Magento is easy! No plug-in's required!
Magento has native support for CDN's and here is a quick guide to getting started...
Step 1
Login to admin panel of Magento, redirect to Store -> Configuration
Step 2
Under General section, select Web -> Base URLs (for http scheme), Modify Base URL for static View Files and Base Url for User media files, with http://<your cdn hostname>/pub/static/ ( this is the default static path for static content, your site static path might be different from this, adjust accordingly.)
Step 3
Scroll down to Base URLs (Secure), do the same things as step 2, but modify the scheme to HTTPS
Step 4
Verify in browser, validate your website static contents is now served from CDN.

Notes:
- You must replace <your cdn hostname> with the URL you have configured in the CDN.net portal.
- If you use custom font in your website, make sure to set Allow CORS for the font files.